18 U.S.C. § 713 (c) states that whoever, except as directed by the United States Senate, or the Secretary of the Senate on its behalf, knowingly uses, manufactures, reproduces, sells or purchases for resale, either separately or appended to any article manufactured or sold, any likeness of the seal of the United States Senate, or any substantial part thereof, except for manufacture or sale of the article for the official use of the Government of the United States, shall be fined under this title or imprisoned not more than six months, or both.